This invention relates to a valve timing control apparatus for an internal combustion engine which is arranged to vary opening and closing timings of an intake valve and an exhaust valve in accordance with an engine driving state.
In recent years, there is provided a valve timing control apparatus for a vehicle provided with an idling stop mechanism. This valve timing control apparatus is arranged to control a relative rotational position of a cam shaft with respect to a timing sprocket to a most retard angle position at an idling stop (after warm-up of the engine), and thereby to decrease an effective compression ratio to decrease a shock of the start. In this way, this valve timing control apparatus attains an Atkinson cycle to improve a startability.
However, in the valve timing control apparatus which can perform the Atkinson cycle, the effective compression ratio becomes small. Accordingly, the start of the engine at the low temperature may become difficult.
A patent document 1 (Japanese Patent Application Publication No. 2011-69288) discloses a valve timing control apparatus which is arranged to lock a valve timing to an intermediate position between a most retard angle position and a most advance angle position at a start of the engine, and thereby to ensure the startability at the low temperature.